بررسي تاثير اسلامپ بتن در ظرفيت كششي شمع بتني درجا

The effect of Concrete Slump of Cast In-Place Piles on Bearing Capacity

با توجه به پيچيدگي اندركنش خاك و شمع و تاثير پارامترهاي متعدد در رفتار متقابل آنها، بهترين روش تخمين ظرفيت باربري شمع‌ها، استفاده از آزمايش بارگذاري است. پژوهشگران با انجام پژوهش‌هاي آزمايشگاهي به بررسي پارامترهاي گوناگون در رفتار شمع پرداخته‌اند. در اين مطالعه، اسلامپ بتن به عنوان يكي از پارامترهاي تاثيرگذار در ظرفيت باربري شمع‌هاي درجا مورد ارزيابي قرار گرفته است. بدين منظور آزمايش بارگذاري بر روي 12 عدد شمع در اندازه‌ي آزمايشگاهي انجام شده است. در اين پژوهش كه بر روي 12 نمونه به طول 120 و قطر 12 سانتي‌متر انجام شده است، شمع‌ها در 4 گروه با اسلامپ‌هاي ثابت 8، 12، 16، و 20 سانتي‌متر مورد آزمايش قرار گرفته اند. طبق مشاهدات تجربي، ظرفيت كششي جداري شمع با اسلامپ بتن تشكيل‌دهنده‌ي بدنه‌ي شمع ارتباط مستقيم دارد، به طوري كه در اسلامپ‌هاي بالاتر مقاومت كششي بيشتري در نمونه ها مشاهده شده است.

Regarding the complexity of soil-pile interaction and the effect of different parameters on their mutual behavior, researchers have found that the best method for evaluating the bearing capacity of piles is the ʹLoading Testʹ. Scientists studied the different parameters of piles, such as pile dimensions, soil characteristics, performance method, type of loading and some other influential parameters in pile behavior, by experimental research. The subject studied in this research is the uplift capacity of a single cast in-place pile in sand with different concrete slumps. These tests were performed on 12 samples with length of 120 cm and diameter of 12 cm. The piles were tested in four groups with constant slumps of 8, 12, 16, 20 cm. In these experiments, PVC pipes were used as casing, and which were pulled out from the ground gradually by the process of pouring concrete. In order to reach structural tensional strength, four longitudinal reinforcement bars with diameter of 8 millimeters were used in the body of the piles. The concrete material used in these tests, such as the particle-size of soil and the consuming cement, were constant for all piles. Different slumps are made by changing the water amount in constant materials. Twelve experimental scale piles with equal characteristics were performed on the site. The aim of these tests is to study the influence of the consistency of concrete on the tensional capacity of the piles, and to show the diagram of the load-settlement to determine the ultimate tensional capacity of the piles. Based on the experimental observations, the tensional strength of a pile is directly related to the concrete slump of the pile, in such a way that at high slump rates, high tensional strength was observed in the samples. Concrete with higher slump rate improves strength parameters in the boundaries between the soil and the pile. It causes more interaction on a greater surface of the pile. It was observed that the difference between the tensional capacity of the piles with the lowest slump rate, and that of the highest slump rate, was about five times.